Fermentation products, such as ethanol, are typically produced by first grinding starch-containing material in a dry-grind or wet-milling process, then degrading the material into fermentable sugars using enzymes and finally converting the sugars directly or indirectly into the desired fermentation product using a fermenting organism. Liquid fermentation products are recovered from the fermented mash (often referred to as “beer mash”), e.g., by distillation, which separate the desired fermentation product from other liquids and/or solids. The remaining fraction is referred to as “whole stillage”. The whole stillage is dewatered and separated into a solid and a liquid phase, e.g., by centrifugation. The solid phase is referred to as “wet cake” (or “wet grains”) and the liquid phase (supernatant) is referred to as “thin stillage”. Wet cake and thin stillage contain about 35 and 7% solids, respectively. Dewatered wet cake is dried to provide “Distillers Dried Grains” (DDG) used as nutrient in animal feed. Thin stillage is typically evaporated to provide condensate and syrup or may alternatively be recycled directly to the slurry tank as “backset”. Condensate may either be forwarded to a methanator before being discharged or may be recycled to the slurry tank. The syrup may be blended into DDG or added to the wet cake before drying to produce DDGS (Distillers Dried Grain with Solubles). An increasing number of ethanol plants extract oil from the thin stillage and/or syrup/evaporated centrate as a by-product for use in biodiesel production or other biorenewable products.
Much of the work in oil recovery/extraction from fermentation product production processes has focused on improving the extractability of the oil from the thin stillage. Effective removal of oil is often accomplished by hexane extraction. However, the utilization of hexane extraction has not seen widespread application due to the high capital investment required. Therefore, other processes that improve oil extraction from fermentation product production processes have been explored.
WO 2011/126897 (Novozymes) discloses processes of recovering oil by converting starch-containing materials into dextrins with alpha-amylase; saccharifying with a carbohydrate source generating enzyme to form sugars; fermenting the sugars using fermenting organism; wherein the fermentation medium comprises a hemicellulase; distilling the fermentation prodct to form whole stillage; separating the whole stillage into thin stillage and wet cake; and recovering oil from the thin stillage. The fermentation medium may further comprise a protease.
It is an object of the present invention to provide improved processes for increasing the amount of recoverable oil from fermentation product production processes.